I confess I don't find them particularly well matched. Martina is an old-fashioned but spunky name with fun nicknames. Daytona is trendy, a place-name most associated with the speedway and NASCAR, which many people (I say this as objectively as possible) consider a "trashy" pastime (or a pastime for trashy people; I don't pay much attention, so I don't know). Besides the stylistic difference, I don't love how similar their endings are: -tona/tina is too matchy for my taste. I suppose the two have a country theme in common: Daytona and NASCAR attract a Southern rural audience, as does country singer Martina McBride... But otherwise, I wouldn't personally pair them.

I think MartinaJade is really nice. I love the possible nicknames (Mara, Mia or Tia, MJ, Marta, besides the more dated Marty or Tina). Daytona Amanda sounds a big sing-songy, though: the same number of syllables, the same ending, the end of Daytona running into the first A of Amanda (Daytonamanda).

I love that Amanda would honor someone close to you. I think something shorter or not ending in -a would work better with MN Amanda. (In fact, I actually think Amanda and Martina would make great sisters!) As a few suggestions, I'd pair sister MartinaJade with:

Martina is sweet, though I personally prefer Marlena (rhymes) because then I don't think "McBride" or "martini" immediately after hearing it. MartinaJade is nice, I have always liked the nickname potential of MJ. Sort of spunky but sweet. Would prefer MarlenaJane over MartinaJade, but that's a personal preference.

Daytona: I have to agree with the other people who've said it's trashy, sorry. I just think Daytona Beach and car racing, which I think would be the biggest association for most people. Also Daytona Amanda runs together for me, since they both end in A and Amanda obviously starts with A. Something like Daytonamanda, or someone stuttering "Daytona Manda".

As sisters... the -tona/-tina thing is really glaring to me. I feel like for the next girl you'd have to look for a -tana or -tena (-tuna? lol) name to round it out.

I like the name Martina, it's underused, spunky and has a plethora of cute nicknames. MartinaJade is lovely.

Daytona I do find trashy, though I'm not a fan of place names in general anyway. I don't know what it is about it, but it just feels a bit, well, trashy. And Daytona Amanda doesn't have the best flow either, the back to back As sort of run.

I don't think they match for sisters at all, they're completely different styles, sorry. And -tona and -tina is a little close for my liking too.

I personally love Daytona, but a lot of people seem to find it trashy? Thoughts? Middle name would be Amanda after my best friend/her godmother. (Not expecting by the way, just collecting)

And what do you think about Martina? With the MN, Jade so MartinaJade. And do they go well together for sisters?

Personally having a daughter named Daytona, I love the name. Anyone who thinks she is "trashy" by hearing her name and not knowing her is ignorant.
That being said, I do not like the double a ending of Daytona and Amanda. I am not a fan of the name Martina-but prefer the name combo on that one.